We have recently shown that inositol is a dietary essential for the gerbil. The primary lesion is a marked accumulation of fat in the mucosal cell of the intestine. The inositol requirement is increased when the diet contains coconut oil, a highly saturated fat, when compared to diets containing unsaturated vegetable oils. A primary objective of these studies is to investigate the metabolic role of inositol. The rate of formation and turnover of various phospholipids in the intestine from animals fed various dietary regimes with and without inositol will be studied using 32PO4 and with fatty acids and inositol labeled with C14. Current evidence suggests that lauric and myristic acids which are primary components of coconut oil accentuate the lesion more than other saturated fatty acids. Data from other conditions in which fatty acid absoption, transport, or metabolism is impaired suggest that there may be a similar pattern of effects relative to the various saturated fatty acids. If so, this suggests that there may be a common point of metabolic control or metabolic defect caused by the saturated fatty acids. The effects of specific fatty acids will be investigated in several of these conditions. The rates of incorporation of the various fatty acids into various lipid fractions and rates of oxidation under the various dietary regimes will be studied as well as changes in the content of various enzymes known to be influenced by changes in the fat content of the diet. Bibliographic references: Frisch, R.E., D.M. Hegsted and K. Yoshinaga. Body weight and food intake at early estrus of rats on a high fat diet. Proc. Natl. Acad. Sci., in Press, October 1975; Hegsted, D.M., A. Gallapher and H. Hanford. Inositol requirement of the Gerbil. J. Nutr. 104: 588, 1974.